With the recent growing awareness of environmental preservation and concern about power shortage, a great deal of attention has been paid to a technique of managing energy consumption in houses, buildings, condominiums, and communities. For example, a house is equipped with so-called home appliance devices such as lighting, air conditioners, and a refrigerator. Recently, an increasing number of houses are equipped with a dispersed power system such as a PV (Photovoltaic Power Generation) system, FC (Fuel Cell), or storage battery. A HEMS (Home Energy Management System) is a system for managing energy consumption of these electrical devices.
For example, visualizing the consumption amount of energy in real time can induce consumers to have “awareness”. This is very effective in energy saving. That is, the first step in energy management is to monitor the statuses of electrical devices. To implement this, it is conceivable to attach a measuring device (sensor) to an outlet or make an electrical device itself have a function of measuring the consumption amount of energy.
However, it takes much cost to attach a measuring device to each outlet and requires much labor to construct a communication means for data acquisition. Although makers have begun to provide electrical devices having measuring devices, most of the existing electrical devices do not have such a function. Demands have arisen for a technique of monitoring the statuses of electrical devices, which can be widely applied to existing electrical devices at low cost.
There is available a technique of monitoring the statuses of electrical devices based on harmonic analysis results on current waveforms or voltage waveforms obtained by a power sensor provided for a power feeder in a house. However, the harmonic generated from an electrical device fluctuates depending on the load, and hence it is difficult to specify the electrical device from a harmonic component. One of the major reasons for this is that an increasing number of home appliance devices (inverter facilities) including inverters in power supply circuits. Inverter facilities include rectifying circuits. Owing to control by a rectifying circuit, the amount and waveform of a current required change in accordance with the load.
That is, the existing method of specifying an electrical device at work based on harmonic analysis results on a mixture of waveforms from various electrical devices includes large errors. The power consumption amount estimated based on a specified electrical device therefore includes a large error. That is, the existing method may include a large estimation error in a power consumption amount and specify a wrong electrical device, thus lacking in reliability.